The invention relates to polymer structures and structural materials.
Polymer structural materials are capable of supporting loads or incurring impact without adversely deforming under these forces. In general, the physical properties required by these applications suggest the use of high density materials, however, high density foams can have rough surfaces and may not be suitable for preventing impact damage to packaged articles or injury due to contact with the hard surface of the material. Softer, low density materials such as polymer foams typically used in these applications can lack sufficient structural support needed in many applications. More specifically, it is desirable for packaging materials to be resilient enough to protect a product, or part of a product, during shipping, but soft enough to prevent damage to the surface of the product, such as marring of a smooth or glossy finish (e.g., that of a painted automobile door). These packaging materials are ordinarily composite structures which have been made of a polyvinylchloride (PVC), corrugated PVC, corrugated polypropylene, corrugated polystyrene, corrugated paper, cardboard, pressboard, or similar stiff material that is lined with a softer material.
A similar situation is encountered in athletic gear, where the material in contact with the user provides support to withstand twisting and pulling forces while avoiding damage to the skin of the user. For example, water sport equipment uses a tough, but soft and flexible, binding mechanism for attaching a piece of sport equipment (e.g., a water ski) to the user. The binding mechanism is ordinarily made up of a solid rubber base--such as high density urethanes, PVC, or rubber or combinations thereof to provide the strength and elongation--having a piece of soft foam attached to the base with an adhesive or glue for the comfort of the user.
In most cases, the structural materials are not easily recycled due to additives (such as adhesives) in the compositions and the nature of some of the other materials used in their construction.